Field of the Invention
The present invention relates to a backlight unit and a liquid crystal display device including the same, and more particularly, to a direct-type backlight unit and a liquid crystal display device including the same.
Discussion of the Related Art
Portable electronic devices, such as mobile terminals and notebook computers, typically include flat panel display devices. Among the flat panel display devices, a liquid crystal display device has advantages, such as highly-developed mass-production technology, easy driving means, low power consumption, high definition resolution, and large screen size. Since the liquid crystals do not emit light, the liquid crystal display device includes a separate light source, such as a backlight unit provided with a light-emitting diode (LED), on a rear surface of a liquid crystal panel to irradiate light toward the surface of the liquid crystal panel to display an image.
Backlight units may be categorized into direct-type backlight units and edge-type backlight units. In a direct-type backlight unit, light sources are arranged below a liquid crystal panel. In an edge-type backlight unit, a light source is arranged to face a side of a light guide plate and a plurality of optical sheets are arranged between the liquid crystal display panel and the light guide plate.
FIG. 1 is a cross-sectional view illustrating a related art liquid crystal display device that includes a direct-type backlight unit. The direct-type backlight unit has a structure where a plurality of optical sheets 5 and a diffuser plate 4 are disposed below a liquid crystal panel 6 and a plurality of light sources 1 are arranged below the diffuser plate 4. Light generated from the light sources 1 is scattered and refracted through the diffuser plate 4 and the optical sheets 5 and then diffused toward an entire surface of the liquid crystal panel 6. The liquid crystal display device also includes a bottom cover 7, a guide panel 8, and a case top 9 to secure the light sources 1, the diffuser plate 4, the plurality of optical sheets 5, and the liquid crystal panel 6.
Particularly, in the related art liquid crystal display device, a support side 3 having a shape inclined with respect to the bottom cover 7 is arranged at both ends of the light source 1. A path of the light generated from the light sources 1 is changed by the support side 3 to increase the light supplied to an edge area of the liquid crystal panel 6. The support side 3 may decrease a deviation between the light supplied to the edge area of the liquid crystal panel 6 as compared with the light supplied to other areas.
FIGS. 2 and 3 are a plane view and a perspective view illustrating an enlarged corner of a related art liquid crystal display device that includes a direct-type backlight unit having a support side 3.
The related art liquid crystal display device that includes a direct-type backlight unit as shown in FIGS. 1 to 3 has problems as follows.
As shown in FIGS. 2 and 3, if distances from a light source 1a arranged to be closest to a corner of a bottom cover 7 to the support side 3 are ‘a’ and ‘b’ respectively, and a minimum distance from the light source 1a to a corner of the support side 3 is ‘c’, a relation of c>a≈b is obtained, which causes a deviation between the amount of light supplied to the corner of the support side 3 as compared with other areas.
FIGS. 4A to 4C illustrate light supplied by a support side 3 of the related art, and an area where darkness occurs due to the light supplied by the support side 3.
FIG. 4A illustrates light supplied to a liquid crystal panel by a support side 3 of the related art, FIG. 4B illustrates an image displayed using the light supplied by the support side 3 of the related art, and FIG. 4C illustrates an image displayed in a videowall based on a liquid crystal display device that includes the support side 3 of the related art.
FIG. 4A illustrates that relatively more light is supplied to the liquid crystal panel 6 if a red color of an image is darker, and thus, FIG. 4A indicates that luminance is high. Relatively less light is supplied to the liquid crystal panel 6 if a green color of an image is darker, and thus, FIG. 4A indicates that luminance is low. Therefore, as shown, it is noted that less light from the light source 1 reaches an area S of FIG. 4A than a periphery area. In this state, if an image is displayed through the liquid crystal panel 6, it is noted that the area S is formed to be relatively darker than the other area as shown in FIG. 4B.
As described above, according to the related art liquid crystal display device, a problem occurs in that a dark area occurs in a corner of the liquid crystal panel due to non-uniform supply of the light.
Meanwhile, the need for a display device having an ultra-large sized area has increased in accordance with the advance of technology. However, because it is difficult to realize an ultra-large sized screen of 100 inches or more in a single display device, a technology called a videowall, multivision, or multiple unit display device based on a plurality of display devices has been developed.
The multivision display device is a display device that realizes a large sized screen by adjacently arranging a plurality of display devices in horizontal and vertical directions. In this way, the multivision display device displays different images in each unit display device or displays one image in each unit display device by dividing one image into several images.
Generally, when an image is displayed by a display device, the most important part of the image is at the center area of the overall display device, and the less important part of the image is in a corner area of the overall display area. However, if an image to be displayed is divided into unit display devices in the multivision display device, the center of the overall display area may correspond to corners of unit display devices. As a result, a dark area may occur in the corner areas of the corresponding unit display devices as described above, thereby resulting in a dark area B at the center of the image, as shown in FIG. 4C.
As described above, when an image to be displayed is divided into unit display devices of a multivision display device, a dark area may occur in important portions of the image, and a user may deem the dark area as a shortcoming in the quality of the display device.